The argumentation presented in this book is the result of a research process initiated at the Design Department of Politecnico di Milano a few years ago, and matured thanks to a doctoral research developed by Francesca Foglieni, which constituted the starting point for the reasoning articulated in these pages. With this text, we share the urgent need to consider evaluation as a strategic activity that should become an integral part of service design, both in theory and practice. We believe it is necessary to support its role as a lever of growth and change in public and private organizations, and to design better services that answer to current social, economic and environmental challenges. This book relies on the idea that service design has the power to trigger meaningful changes, but for this to happen new directions need to be envisioned and explored for the discipline to evolve. Applied research projects, teaching activities and conversations with expert colleagues and professionals have also been fundamental to the full development of our vision. Our purpose is to open a debate on a topic that still deserves further investigations in the disciplinary field as well as in comparison with other disciplines. We hope that other researchers will share the hypotheses presented here and will prosecute the discussion with passion, dedication and relevant contributions.